A rotating friction pin is the central tool with friction stir welding (FSW), the innovative seam welding process that Grenzebach has developed for lightweight metals such as aluminium and its alloys. Through friction and pressure, the pin generates the process heat required to make the metal malleable, which is then stirred along the contact point by the rotational action of the friction pin. Without the need for the addition of welding wire or inert gas, this creates a solid joint that is characterised by its long-term stability and its resistance to distortion.
A requirement for this result is that the friction pin behaves as expected. Accurate tensile and pressure forces are critical for achieving the correct degree of deformation of the metal. Traditionally, a quality check was carried out by the machine operator, who would visually assess the welded seam after the FSW process. This was a time-consuming procedure and its success was heavily dependent on the personal know-how of the operator.
The weld seams created by the friction pin are characterised by their high quality, especially in combination with real-time monitoring
As a committed pioneer in the area of Industry 4.0, Grenzebach is already making use of smart data analysis processes that enable accurate forecasting. And for this purpose, they use a tailored Industrial Analytics solution from Weidmüller. “Our Analytics software, which has been customised to meet the needs of Grenzebach, compares the forces recorded at the sensors during the weld process with an ideal reference data record. As soon as the system detects a deviation that lies outside the defined parameters, the machine operator is notified and immediately knows that something isn’t right with the weld process. This eliminates the need for manual checks of every weld seam,” explains Dr Daniel Kress, Data Scientist responsible for the project at Weidmüller.
Working together with Grenzebach engineers, Weidmüller analysed over 100 weld seams for their relevance and evaluated them using smart data analysis processes, in order to create the reference models. A significant element of the analyses was provided by the know-how coming from Grenzebach. The Weidmüller software may well be able to predict a fault with a certain degree of probability, but to do so it always needs to have been classified beforehand. Only Grenzebach can determine whether an anomaly should actually be classified as a critical error or not.
As well as carrying out quality control checks on the weld seams, the Analytics software also records the process parameters of each part that is produced, thereby producing complete documentation. This is a significant benefit not only from the legal aspect but also in terms of traceability and reproducibility. The system also delivers a timely warning if a replacement of the welding pin would be advisable. Armed with this information, the machine operator can plan the maintenance schedule in such a way that any downtime is avoided. “Alongside the minimising of waste that can result from a tool breakage, an important factor, particularly in machinery and plant engineering, is the availability of the machines,” emphasises Kress.
Technology developer Dr Carlos Paiz Gatica explains how the anomaly detection works: the comparison of a reference model with the current process facilitates real-time quality assessment
High-tech specialists Grenzebach can see several more advantages in respect of its business model going forward: “Firstly, we can offer our customers very accurate and quantifiable quality control as well as giving them a forecast about possible equipment downtime, enabling them to save on resources and costs. At the same time, we are in a position to implement data-driven services and effectively to use the product quality or the availability of the equipment as selling arguments,” explains Michael Sieren, FSW Sales Manager at Grenzebach.
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Published in November 2017
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